So how do the Hue light switches work?

Hue light switches (well, the ones I have) simply stick on the wall with no wiring.

The _real_ light switch is permanently on, and the _hue_ light switch sends a beacon to the hub to turn the configured lights on/off (the light bulb socket is always-on)

No, some switchers and dimmers can also control lights without a hub present. Some products come as a paired bulb and switch, with only an optional suggestion that you later extend into the ecosystem.

Not all, IKEA Trådfri works fully hub-less by default.

TIL I can bind my remotes to my Hue bulbs, and they work without the coordinator.

This is not true. Look into Zigbee binding, it works when the coordinator is offline.

I'm using that as a backup solution in my house. All lights are zigbee, permanently powered, normally most are controlled automatically by presence sensors. But I have a couple of Zigbee remotes in a box that are bound directly to the lights to use in case my home automation system is down.

I'd modify my comment if I could. Bound some remotes to some hue bulbs, proving myself wrong.